Flow control valves are a well-known and integral part of most irrigation systems. A typical example can be seen in U.S. Pat. No. 6,394,413 to Lohde et al., hereby incorporated by reference.
These valves control the flow of water through an upstream pipe and thereby turn sprinklers fed by the pipe on and off. Such valves are usually remotely actuated by control signals sent from an automated irrigation controller. Often these control signals are electric current sent from the controller to a solenoid in the valve which ultimately controls whether the valve is open or closed.
Solenoid-activated diaphragm-operated valves for use in irritation systems are well known. One example can be seen in U.S. Pat. No. 6,394,413 to Lohde et al., previously incorporated by reference.
This style of valve has a closure member with a sealing surface which moves against or away from an annular seat to close or open the valve. Integral to the closure member is a diaphragm positioned to seal off an upper portion of the valve. A metering passage allows water to enter the upper portion and thereby build up pressure to maintain the closure member in a closed position.
When the valve is to be opened, the fluid pressure in the upper portion is relieved by bleeding fluid out of the diaphragm chamber through a manual valve or by a remotely operated solenoid valve. Relieving this pressure allows the closure member to move upwards as water passes through the valve. The discharged water is conveniently released into the passageway, beyond the primary flow-controlling sealing member, near the outlet port.
Over time, dirt, corrosion and other debris within the water can block or clog the metering passage. This blockage can prevent water and therefore water pressure from building up within the upper portion, thereby preventing the valve from closing.
U.S. Pat. Nos. 5,996,608 and 6,575,307 have addressed this problem by providing a longitudinally moving wiper blade to scrape off debris from a filter screen over the metering passage. The filter screen prevents debris, coarse enough to block the metering passage, from blocking the passage. However, these designs fail to effectively clean the filter screen, often passing over or further embedding the debris in the screen. Further, these prior art designs rely on movement of a scraping mechanism axially only when the valve is turned on or off, further diminishing any cleaning capability.
Therefore, what is needed is a debris-tolerant valve that can better prevent the metering passage from clogging and thereby maintain free flow through the metering passage.